I. Field of the Invention
The present invention is directed generally to portable diagnostic systems based on electrochemical determinations in biological samples in which the control of sample temperature is important to analytical accuracy. More particularly, the invention concerns a system for controlling the temperature in a removable disposable cartridge sampling unit for use with a portable diagnostic system. The system achieves rapid heating to and accurate control at a predetermined set point without the need for contact between any temperature measuring device and the disposable cartridge unit itself.
II. Related Art
Methods and devices utilized for determining concentrations of electroactive species in solution using electrochemical or electrolytic methods such as, for example, the determination of pO.sub.2, pCO.sub.2 and electrolytes in blood samples, are well known. These instruments typically include a pair of electrochemical half cells, one of which is used as the sensor or sample half cell and the other as a reference electrode or a reference half cell. As is the case with any concentration determination of dissolved gaseous species in a liquid, the temperature at which the electrochemical determination is made needs to be known. Traditionally, blood gas determinations, for example, have been made utilizing permanently installed laboratory instrumentation to which samples are brought for analysis. Of course, in such instruments the temperature at which the sample is analyzed can be readily controlled as by a constant temperature oven, or the like. This, of course, is not practical in the case of a small portable device.
Thus, there remains a need for an inexpensive approach to controlling the sample temperature in a portable blood gas analyzer or other such instrument that is easily manufactured and rapidly stabilizing and accurate. Accordingly, it is a primary object of the present invention to provide a temperature control system for use in conjunction with a portable analytical device which is simple, reacts rapidly and accurately controls sample temperature.
It is a further object of the present invention to provide a non-contact temperature measurement system for a disposable test cartridge, so that prolonged or repeated use will not physically wear components to a state of unreliability.
Yet another object of the present invention is to provide a temperature control system for a disposable cartridge electrochemical cell sampling device in which the disposable cartridge carries its own inexpensive internal resistive heating element to heat the sample environment. A still further object of the invention is to provide a temperature control system for such a disposable cartridge which uses a temperature sensor that need not be directly connected to the disposable cartridge.
These and other objects will become apparent to those skilled in the art in accordance with the descriptions and drawings herein.